In a steam turbine, the leakage of the turbine driving steam to the outside is typically prevented by a gland sealing system. The system typically comprises a series of at least three labyrinth packing segments located along the turbine rotor in the region where the rotor exits the turbine casing. A gland carrier casing supporting the sealing rings may form at least two chambers with the turbine casing The chamber(s) enables the ejection of a mixture of steam- air and an injection of steam, when there is more than one chamber in the upstream higher pressure chamber. Each of these chambers are separated by sealing rings or labyrinth packing segments.
As system with not less than two chambers may, for example, comprise a first chamber in which a mixture of steam/air is injected and a second chamber with in which steam is either injected or ejected depending on the operating mode. As an example, the first chamber could operate at a pressure about 0.95 bar while the second chamber could operate at a pressure about 1.15 bar.
In a typically arrangement, each of the packing segments is mounted on a gland carrier casing of the turbine. In the case where the gland carrier casing component on which the sealing rings are mounted additionally forms part of the steam turbine exhaust, the turbine casing component may be exposed to local gland chambers temperature as well as steam turbine exhaust temperature. In the case of a high and intermediate pressure steam turbine having a high pressure shaft end gland system and an intermediate pressure shaft end gland system, the temperature gradient may be 110° C. on the high pressure side and 70° C. on the intermediate pressure side. This may result in the turbine casing component being exposed to large thermal stresses.